IOP fluctuation does not predict visual field progression in glaucoma

A recent study has found no evidence supporting the association of intraocular pressure (IOP) fluctuation, as measured in clinical practice, with visual field (VF) progression in patients with glaucoma.

Other IOP aspects, such as mean IOP and peak IOP, appear more informative, whereas ocular pulse pressure may be independently associated with faster glaucoma progression.

This randomized, placebo-controlled trial included participants with five or more VFs (217 treatment and 213 placebo). The investigators used linear mixed models to examine the relationship between IOP metrics and VF progression rates (mean deviation [MD] and five fastest locations).

Fluctuation variables were as follows: mean Pascal ocular pulse amplitude (OPA), standard deviation (SD) of diurnal Goldmann IOP (diurnal fluctuation), and SD of Goldmann IOP at all visits (long-term fluctuation). Values of fluctuation were normalized for mean IOP to make them independent from the mean IOP.

The investigators then combined the principal component analysis with correlated nonfluctuation IOP metrics (ie, baseline, peak, mean, supine, and peak phasing IOP) and included principal component 1 (PC1) as a covariate. Interactions between covariates and time from baseline simulated the effect of the variables on VF rates. Separate analyses were carried out in the two treatment arms.

In patients who received placebo, PC1 showed a significant association with the MD rate (estimate, ‒0.19 dB/year; p<0.001) but normalized IOP fluctuation metrics did not. In the treatment arm, no variable significantly correlated with MD rates.

For the fastest five locations in the placebo group, progression rates correlated with PC1 (estimate, ‒0.58 dB/year; p<0.001), central corneal thickness (estimate, 0.26 dB/year; p=0.01), and normalized OPA (estimate, ‒3.50 dB/year; p=0.001) but not with normalized diurnal and long-term IOP fluctuations.

In the treatment group, only PCA (estimate, ‒0.27 dB/year; p=.028) showed a significant association with progression rates.